Messages in this thread Patch in this message | | | From | Tianyi Liu <> | Subject | [PATCH] Introduce callchains for guests | Date | Thu, 31 Aug 2023 16:09:02 +0800 |
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This patch serves as the foundation for enabling callchains for guests, (used by `perf kvm`). This functionality is useful for me, and I noticed it holds the top spot on the perf wiki TODO list [1], so I'd like to implement it. This patch introduces a `perf_callchain_guest` interface, which different architectures can implement according to their own specifications.
This is part of a series of patches. Since these patches are spread across various modules like perf, kvm, arch/*, I plan to first submit some foundational patches and gradually submit the complete implementation. The full implementation can be found at [2], and it has been tested on an x86_64 machine.
Since perf tools currently do not support callchain types with PERF_CONTEXT_GUEST*, I temporarily used PERF_CONTEXT_KERNEL for ease of testing and validation. This will be rectified once the perf tools patches are applied.
Furthermore, do you think it's necessary to introduce a new guest filter in the parameters of `get_perf_callchain`? Alternatively, should we add two separate filters, `guest_user` and `guest_kernel`, to make these filters entirely independent?
This is my first time submitting a patch for a new feature in the kernel, and I would greatly appreciate any suggestions.
[1] https://perf.wiki.kernel.org/index.php/Todo [2] https://github.com/i-Pear/linux/pull/2/files
Signed-off-by: Tianyi Liu <i.pear@outlook.com> --- kernel/events/callchain.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 1273be84392c..eacb6ccf7034 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -45,6 +45,10 @@ __weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry, { } +__weak void perf_callchain_guest(struct perf_callchain_entry_ctx *entry) +{ +} + static void release_callchain_buffers_rcu(struct rcu_head *head) { struct callchain_cpus_entries *entries; @@ -183,6 +187,7 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, struct perf_callchain_entry *entry; struct perf_callchain_entry_ctx ctx; int rctx; + unsigned int guest_state; entry = get_callchain_entry(&rctx); if (!entry) @@ -194,6 +199,26 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, ctx.contexts = 0; ctx.contexts_maxed = false; + guest_state = perf_guest_state(); + if (guest_state) { + if (add_mark) { + if (guest_state & PERF_GUEST_USER) + /* + * TODO: Change this to PERF_CONTEXT_GUEST_USER, + * which is currently not recognized by perf utils. + */ + perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); + else + /* + * TODO: Change this to PERF_CONTEXT_GUEST_KERNEL, + * which is currently not recognized by perf utils. + */ + perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); + } + perf_callchain_guest(&ctx); + goto exit_put; + } + if (kernel && !user_mode(regs)) { if (add_mark) perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); -- 2.34.1
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